The present invention relates to the preparation of a hydroxyalkyl phosphonic acid using an acid functionalized ion exchange resin.
The phosphonic acid monomer 2-(methacryloyloxy)alkyl phosphonic acid (MEP) is useful in the preparation of binders that adsorb to the surfaces of TiO2 particles. Latexes functionalized with MEP have shown excellent heat age stability, hiding, and tint strength. MEP can be prepared by reacting hydroxyethyl phosphonic acid with methacrylic acid at a high temperature and sub-atmospheric pressure. The hydroxyethyl phosphonic acid is traditionally prepared by reacting the corresponding alkylphosphonate with a strong acid such as HCl. Unfortunately, this method is costly, corrosive, and toxic, resulting in the production of toxic alkyl chlorides such methyl chlorides as byproducts. It would therefore be desirable to find a safer and more economical process for preparing the hydroxyethyl phosphonic acid precursor to MEP.